// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "ui/gfx/animation/slide_animation.h"

#include <math.h>

namespace gfx {

// How many frames per second to target.
static const int kDefaultFrameRateHz = 60;

// How long animations should take by default.
static const int kDefaultDurationMs = 120;

SlideAnimation::SlideAnimation(AnimationDelegate* target)
    : LinearAnimation(kDefaultFrameRateHz, target)
    , target_(target)
    , tween_type_(Tween::EASE_OUT)
    , showing_(false)
    , value_start_(0)
    , value_end_(0)
    , value_current_(0)
    , slide_duration_(kDefaultDurationMs)
{
}

SlideAnimation::~SlideAnimation()
{
}

void SlideAnimation::Reset()
{
    Reset(0);
}

void SlideAnimation::Reset(double value)
{
    Stop();
    showing_ = static_cast<bool>(value == 1);
    value_current_ = value;
}

void SlideAnimation::Show()
{
    // If we're already showing (or fully shown), we have nothing to do.
    if (showing_)
        return;

    showing_ = true;
    value_start_ = value_current_;
    value_end_ = 1.0;

    // Make sure we actually have something to do.
    if (slide_duration_ == 0) {
        AnimateToState(1.0); // Skip to the end of the animation.
        return;
    } else if (value_current_ == value_end_) {
        return;
    }

    // This will also reset the currently-occurring animation.
    SetDuration(static_cast<int>(slide_duration_ * (1 - value_current_)));
    Start();
}

void SlideAnimation::Hide()
{
    // If we're already hiding (or hidden), we have nothing to do.
    if (!showing_)
        return;

    showing_ = false;
    value_start_ = value_current_;
    value_end_ = 0.0;

    // Make sure we actually have something to do.
    if (slide_duration_ == 0) {
        AnimateToState(0.0); // Skip to the end of the animation.
        return;
    } else if (value_current_ == value_end_) {
        return;
    }

    // This will also reset the currently-occurring animation.
    SetDuration(static_cast<int>(slide_duration_ * value_current_));
    Start();
}

void SlideAnimation::SetSlideDuration(int duration)
{
    slide_duration_ = duration;
}

double SlideAnimation::GetCurrentValue() const
{
    return value_current_;
}

void SlideAnimation::AnimateToState(double state)
{
    if (state > 1.0)
        state = 1.0;

    state = Tween::CalculateValue(tween_type_, state);

    value_current_ = value_start_ + (value_end_ - value_start_) * state;

    // Implement snapping.
    if (tween_type_ == Tween::EASE_OUT_SNAP && fabs(value_current_ - value_end_) <= 0.06)
        value_current_ = value_end_;

    // Correct for any overshoot (while state may be capped at 1.0, let's not
    // take any rounding error chances.
    if ((value_end_ >= value_start_ && value_current_ > value_end_) || (value_end_ < value_start_ && value_current_ < value_end_)) {
        value_current_ = value_end_;
    }
}

} // namespace gfx
